The invention relates to a new type of polymer compound comprising a fully fluorinated thermoplastic material, in particular melt processible PTFE (m-PTFE) as well as a proportion of at least one additional high performance polymer which is different hereto and selected from the group of polyether ketone (PEK), polyether ether ketone (PEEK) and polyether aryl ketone (PEAK) as well as copolymers and derivatives of these polymers and copolymers, wherein the compound displays a homogeneous distribution of the proportions of the polymers.
The use of conventional PTFE in compounds with polyether ether ketones is known per se. Such compounds are produced by mixing the various polymers in powder form and, depending on the type of the main component, by subsequently pressure sintering or extruding them. If PTFE is the main component, the amount of polyether ether ketone is limited to a maximum of approximately 30% by weight. In the case where the main ingredient is polyether ether ketone, the amount of PTFE is limited to a maximum of 20% by weight.
In the first case, the mechanical properties, such as, e.g., the breaking stress and the breaking elongation, are noticeably worse with amounts of PEEK of above 20% by weight since the high proportion of PEEK which acts as a type of filler material in the PTFE matrix disrupts the cohesion of the PTFE matrix significantly.
In the second case, greater proportions of PTFE result first of all in the compound with the main ingredient of PEEK no longer being processible with the conventional methods of thermoplastic processing.
If the so-called hot compression molding process is used, somewhat greater amounts of PTFE up to approximately 30% by weight are possible. With even greater proportions of PTFE, the PEEK matrix will be significantly disrupted and the mechanical material properties drop drastically.
With these compounds, the fact that they cannot be obtained with a homogeneous melt structure is unsatisfactory. The improvements in the properties of the respective main components, which are aimed for by means of the compounding with the other polymer content, can, therefore, be achieved at the most to a small extent.
For these reasons, compounds with mixing ratios located therebetween are not available.
Typically, in the case of compounds with the main ingredient PEEK, the PTFE particles still remain as individually recognizable grains even after the thermoplastic processing with the methods described. The particles of the PTFE component do melt completely at the processing temperatures customary for PEEK of, typically, 370° C.±10° C. but there is no adequate mixing of the two polymer melts with the customary treatment times of, for example, 15 to 60 min on account of the high melt viscosity of the PTFE which is, typically, approximately 1010 to 1013 Pa×s at 380° C.
In the case of compounds with the main ingredient PTFE, the PEEK particles remain as individual particles even after undergoing the processing methods customary for PTFE although both components do melt at the sintering temperatures customary for PTFE of approximately 360 to 380° C. but no or only slight intermixing effects occur, on the one hand, on account of the high melt viscosity of the PTFE and, on the other hand, on account of the fact that no shearing forces act on the polymer melt during these processing methods typical for PTFE.
The object of the invention is to provide polymer compounds which are improved with respect to their properties compared to conventional PTFE, on the one hand, and compared to the additional high performance polymer or polymers, on the other hand.